A novel region referred to as the POU-domain is present in two tissue-specific transcription factors, Pit-1 and Oct-2, that activate expression of genes specifying pituitary and lymphocyte phenotypes. We report the identification of multiple new members of a large family of POU-domain genes expressed in adult brain, and document that all the known mammalian POU-domain genes, including Pit-1 and Oct-2, are expressed widely in the developing nervous system.

The steady-state level and metabolic half-life of retinoblastoma tumor suppressor protein pRB are decreased in cells that express high-risk human papillomavirus (HPV) E7 proteins. Here we show that pRB degradation is a direct activity of E7 and does not reflect a property of cell lines acquired during the selection process for E7 expression. An amino-terminal domain of E7 that does not directly contribute to pRB binding but is required for transformation is also necessary for E7-mediated pRB degradation. Treatment with inhibitors of the 26S proteasome not only blocks E7-mediated pRB degradation but also causes the stabilization of E7. Mutagenic analyses, however, reveal that the processes of proteasomal degradation of E7 and pRB are not linked processes. HPV type 16 E7 also targets the pRB-related proteins p107 and p130 for destabilization by a proteasome-dependent mechanism. Using the SAOS2 flat-cell assay as a biological indicator for pRB function, we demonstrate that pRB degradation, not solely binding, is important for the E7-induced inactivation of pRB.Human papillomaviruses (HPVs) are DNA viruses with small circular genomes that cause epithelial hyperplasias ranging from benign papillomas (warts) to premalignant lesions that can progress to squamous cell carcinomas (reviewed in reference 25). There are over 100 different HPV types, approximately 30 of which specifically infect anogenital tract mucosa. These HPVs are classified as low risk or high risk, depending on the clinical prognosis of the lesions they cause. Low-risk HPVs, such as HPV type 6 (HPV-6) and HPV-11, cause condylomata acuminata (genital warts), while high-risk HPVs, including HPV-16 and HPV-18, are associated with squamous intraepithelial lesions that can progress to cervical carcinomas. Integration of the HPV genome into a host cell chromosome is a frequent event during malignant progression and results in the consistent but dysregulated expression of the HPV E6 and E7 proteins (reviewed in reference 55).High-risk HPV E6 proteins target tumor suppressor protein p53 for ubiquitin-mediated proteasomal degradation by interacting with and reprogramming the E6-AP ubiquitin ligase (38, 39, 51). E6-mediated degradation of p53 compromises the ability of the host cell to engage cell cycle checkpoints and apoptotic responses (33). High-risk HPV E7 oncoproteins target retinoblastoma tumor suppressor protein pRB (19). Highrisk HPV E7 proteins interact with pRB at a higher efficiency than do low-risk HPV E7 proteins (22,34). Interaction of E7 with hypophosphorylated pRB causes the disruption of growth-suppressive pRB-E2F complexes (10), promoting the G 1 -S cell cycle transition. E7-mediated cellular transformation correlates with pRB binding (22); however, there are mutations in E7 that impair cellular transformation and immortalization without affecting pRB binding (4,8,20,28,35). Furthermore, the E7 protein of HPV-1a, a low-risk cutaneous HPV, can interact with pRB and transactivate E2F-dependent promoters with the same efficiency as can high-risk ...

BackgroundSub-therapeutic antibiotics are widely used as growth promoters in the poultry industry; however, the resulting antibiotic resistance threatens public health. A plant-derived growth promoter, Macleaya cordata extract (MCE), with effective ingredients of benzylisoquinoline alkaloids, is a potential alternative to antibiotic growth promoters. Altered intestinal microbiota play important roles in growth promotion, but the underlying mechanism remains unknown.ResultsWe generated 1.64 terabases of metagenomic data from 495 chicken intestinal digesta samples and constructed a comprehensive chicken gut microbial gene catalog (9.04 million genes), which is also the first gene catalog of an animal’s gut microbiome that covers all intestinal compartments. Then, we identified the distinctive characteristics and temporal changes in the foregut and hindgut microbiota. Next, we assessed the impact of MCE on chickens and gut microbiota. Chickens fed with MCE had improved growth performance, and major microbial changes were confined to the foregut, with the predominant role of Lactobacillus being enhanced, and the amino acids, vitamins, and secondary bile acids biosynthesis pathways being upregulated, but lacked the accumulation of antibiotic-resistance genes. In comparison, treatment with chlortetracycline similarly enriched some biosynthesis pathways of nutrients in the foregut microbiota, but elicited an increase in antibiotic-producing bacteria and antibiotic-resistance genes.ConclusionThe reference gene catalog of the chicken gut microbiome is an important supplement to animal gut metagenomes. Metagenomic analysis provides insights into the growth-promoting mechanism of MCE, and underscored the importance of utilizing safe and effective growth promoters.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0590-5) contains supplementary material, which is available to authorized users.

Investigation of the large POU domain family of developmental regulators has revealed a molecular mechanism by which highly related transcription factors sharing common DNA-binding motifs act to functionally discriminate their cognate DNA sequences. Studies of two classes of neuron-specific POU domain factors {III and IV) indicate that functional specificity on their native response elements is achieved by accommodating different nucleotide spacing between variably oriented bipartite core DNA-binding motifs. The preferred orientation of the POU-specific domain of the neuronal factors on their native response elements appears to be opposite that of Pit-1 and Oct-1. Members of POU-III {Brn-2) class exhibit remarkable flexibility in DNA site recognition {tolerating core motifs spaced by 0, 2, or 3 nucleotides), whereas POU-IV IBm-3) class is highly constrained {tolerating core motifs with a spacing of 3 nucleotides). The molecular determinant of the constraint in DNA site selection appears to be imparted by 3 amino acid residues in the amino-terminal basic region in concert, with helix 2 of the POU homeo domain which together are involved in minor groove and possibly phosphate backbone contacts. Similar mechanisms may underlie differential flexibility in spacing and orientation for diverse families of transcription factors.

A novel, structurally distinct POU-domain protein has been identified that inhibits activation by another positive POU-domain regulator of neuron-specific transcription units. Two Drosophila POU-domain proteins, I-POU and Cf1-a, are coexpressed in overlapping subsets of neurons during development. Because I-POU lacks two basic residues in the N terminus of its homeodomain, it cannot bind DNA, but it does form a stable heterodimeric complex with Cf1-a, preventing Cf1-a from binding to DNA recognition elements and from transactivating the dopa-decarboxylase gene. The inhibition by I-POU provides a potential strategy by which the activation of genes in development is controlled by a homeodomain-containing protein that does not bind DNA.

Intracellular Vitamin C (VC) is maintained at high levels in the developing brain by the activity of sodium-dependent VC transporter 2 (Svct2), suggesting specific VC functions in brain development. A role of VC as a cofactor for Fe(II)-2-oxoglutarate-dependent dioxygenases has recently been suggested. We show that VC supplementation in neural stem cell (NSC) cultures derived from embryonic midbrains greatly enhanced differentiation towards midbrain-type DA (mDA) neurons, the neuronal subtype associated with Parkinson’s disease. VC induced gain of 5-hydroxymethylcytosine (5hmC) and loss of H3K27m3 in DA phenotype gene promoters, which are catalyzed by Tet1 and Jmjd3, respectively. Consequently VC enhanced DA phenotype gene transcriptions in the progenitors by Nurr1, a transcription factor critical for mDA neuron development, to be more accessible to the gene promoters. Further mechanism studies including Tet1 and Jmjd3 knockdown/inhibition experiments revealed that both the 5hmC and H3K27m3 changes, specifically in the progenitor cells, are indispensible for the VC-mediated mDA neuron differentiation. We finally show that in Svct2 knockout mouse embryos, mDA neuron formation in the developing midbrain decreased along with the 5hmC/ H3k27m3 changes. These findings together indicate an epigenetic role of VC in midbrain DA neuron development.

The POU domain gene family of transcription factors share a conserved bipartite DNA binding domain, and exhibit distinct temporal and spatial patterns of expression during development, particularly in the forebrain. A cDNA encoding a new member of the POU‐III class of the POU domain gene family, referred to as Brn‐4, was isolated from a rat hypothalamic cDNA library. Like other mammalian POU‐III genes previously characterized (Brn‐1, Brn‐2, Tst‐1), Brn‐4 transcripts are initially widely expressed at all levels of the developing neural tube, but in contrast to other previously described POU‐III genes, are subsequently restricted to only a few regions of the adult forebrain, including the supraoptic and paraventricular nuclei of the hypothalamus. Brn‐4 was shown to bind to DNA sequences containing the octamer motif and to trans‐activate promoters containing this DNA binding motif, based on the actions of a unique N‐terminal information. This ontogenic pattern of Brn‐4 expression in concert with that of Oct‐2 and Pit‐1, indicates that certain POU domain genes potentially exert their primary functions widely during early neural development, and in a very limited set of neurons in the mature brain.

Tst-1, a member of the POU domain gene family, is expressed in specific neurons and in myelinating glia in the mammalian nervous system. Bacterially expressed Tst-1 binds specifically to the promoter of the gene encoding myelin protein P0, a Schwann cell surface adhesion molecule. In cotransfection assays, Tst-1 can specifically repress the P0 promoter. The N-terminal part of Tst-1 protein is highly glycine- and alanine-rich, a structural feature shared by the helix-loop-helix protein TFEB.